What was the sign of Jonah?

“What was the sign of Jonah?” is a book by Ahmed Deedat who tries to challenge one of claims made in the Jewish and Christ scriptures to prophesy about Jesus Christ, making clear their errors. He noted that Jesus responded to the request of the Jewish scholars to provide proof of the truth of his invitation: “And there shall no sign (no miracle) be given to it, but the sign (miracle) of the prophet Jonas: for as Jonas was three days and three nights in the whale’s belly; so shall the son of man be three days and three nights in the heart of the earth.” (Matthew 12: 39-40). Citing biblical evidences, Deedat proved that this resemblance is by no means true and that the various justifications mentioned over years have serious flaws.